Press the Mission Control key on your Apple keyboard, or press Control–Up Arrow.

In OS X El Capitan, drag a window to the top of the screen.

Mission Control shows the Spaces bar at the top of the screen, and below it all of the windows that are open on your desktop. The Spaces bar includes these spaces, which you can view by moving your pointer to the top of the Mission Control screen:

Add a space

Add a desktop space: Click the Add Space icon on the right side of the Spaces bar, or drag a window to that icon.

Add a full-screen space: If an app supports full-screen view, you can create a full-screen space for that app by dragging its window to an empty area of the Spaces bar. The new space shows the name of that app. Click the space to see the app in full screen.

Move a window to a space

Move a window to a desktop space: Drag the window to that space in the Spaces bar.

Move a window to a full-screen space (Split View): If an app supports Split View, you can drag its window to a full-screen space in the Spaces bar. The combined space shows the names of both apps. Click the space to see both apps in Split View.

If your windows are grouped by application, an app icon appears at the bottom of each group of application windows. Drag the icon to move all of the app's windows at the same time. To turn on this feature in OS X El Capitan, choose Apple menu > System Preferences, click Mission Control, then select “Group windows by application.”

Switch to another space

Use any of these methods to switch from your current space to another space: